If you truly want to experience the original Horizon festival on your PC, here are the methods:

While you are looking for an "Apunkagames updated" version, it is important to note:

to make it run smoothly on modern hardware. System Requirements (Estimated)

Heard about an “updated” Forza Horizon 1 PC download on Apunkagames? Be careful — FH1 was never released for PC. Those files are either scams or broken emulator setups.